1. Field of the Invention
The present invention relates to a zoom lens composed of three groups suitable for a lens-shutter camera or the like and, in particular, to a three-group zoom lens incorporated in a camera used by professionals or high-standard amateurs for which a high image quality is required.
2. Description of the Prior Art
Recently, as a lens system used in a lens-shutter camera, the one equipped with a zoom lens has been constituting the mainstream. Since it is required for such a zoom lens to have a compact size to begin with, a two-group zoom lens of a telephoto type refracting power arrangement comprising a first lens group having a positive refracting power and a second lens group having a negative refracting power has been put into practical use.
Meanwhile, since lens-shutter cameras used by professionals or high-standard amateurs require a high image quality in general, known as a zoom lens incorporated in such a camera is a three-group zoom lens in which the above-mentioned first lens group is divided into two positive lens groups, so as to yield a refracting power group arrangement of positive, positive, and negative as a whole, thereby securing a favorable image quality.
Known as a typical technique for achieving a high image quality of a zoom lens while reducing its size is the one in which the number of lens sheets is increased. When simply increasing the number of lens sheets, however, the lens as a whole becomes larger in size. In particular, when a wider angle and a higher image quality are to be obtained, the front lens enhances its diameter so that it becomes difficult for the lens to be built into the main body of the camera.